From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753281AbdK3QCN (ORCPT ); Thu, 30 Nov 2017 11:02:13 -0500 Received: from mail-wr0-f195.google.com ([209.85.128.195]:44900 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752507AbdK3QCK (ORCPT ); Thu, 30 Nov 2017 11:02:10 -0500 X-Google-Smtp-Source: AGs4zMaLRYJuQxbYphqhQV1ClYYcuwJfvqx8vZ5bAfFWXOt/ABOgrPkizomCuB0yUPAmH6weFSqErw== Date: Thu, 30 Nov 2017 17:02:05 +0100 From: Juri Lelli To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Peter Zijlstra , "Rafael J . Wysocki" , Viresh Kumar , Vincent Guittot , Dietmar Eggemann , Morten Rasmussen , Todd Kjos , Joel Fernandes Subject: Re: [PATCH v3 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE enter Message-ID: <20171130160205.GH9903@localhost.localdomain> References: <20171130114723.29210-1-patrick.bellasi@arm.com> <20171130114723.29210-2-patrick.bellasi@arm.com> <20171130131222.GA9903@localhost.localdomain> <20171130154111.GC31247@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171130154111.GC31247@e110439-lin> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/11/17 15:41, Patrick Bellasi wrote: > On 30-Nov 14:12, Juri Lelli wrote: > > Hi, > > > > On 30/11/17 11:47, Patrick Bellasi wrote: > > > > [...] > > > > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > > > index 2f52ec0f1539..67339ccb5595 100644 > > > --- a/kernel/sched/cpufreq_schedutil.c > > > +++ b/kernel/sched/cpufreq_schedutil.c > > > @@ -347,6 +347,12 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time, > > > > > > sg_cpu->util = util; > > > sg_cpu->max = max; > > > + > > > + /* CPU is entering IDLE, reset flags without triggering an update */ > > > + if (unlikely(flags & SCHED_CPUFREQ_IDLE)) { > > > + sg_cpu->flags = 0; > > > + goto done; > > > + } > > > > Looks good for now. I'm just thinking that we will happen for DL, as a > > CPU that still "has" a sleeping task is not going to be really idle > > until the 0-lag time. > > AFAIU, for the time being, DL already cannot really rely on this flag > for its behaviors to be correct. Indeed, flags are reset as soon as > a FAIR task wakes up and it's enqueued. Right, and your flags ORing patch should help with this. > > Only once your DL integration patches are in, we do not depends on > flags anymore since DL will report a ceratain utilization up to the > 0-lag time, isn't it? Utilization won't decrease until 0-lag time, correct. I was just wondering if resetting flags before that time (when a CPU enters idle) might be an issue. > > If that's the case, I would say that the flags will be used only to > jump to the max OPP for RT tasks. Thus, this patch should still be valid. > > > I guess we could move this at that point in time? > > Not sure what you mean here. Right now the new SCHED_CPUFREQ_IDLE flag > is notified only by idle tasks. That's the only code path where we are > sure the CPU is entering IDLE. > W.r.t. the possible issue above, I was thinking that we might want to reset flags at 0-lag time for DL (if CPU is still idle). Anyway, two distinct set of patches. Who gets in last will have to ponder the thing a little bit more. :) Best, Juri